A Simple, Illustrated Introduction To Single Infusion Mash Temperatures

Sometimes it seems that the more you learn about brewing the less you know. There are so many variables that you can’t possibly manage all of them at once.

However, there’s one thing that’s easily controlled and can alter the profile of your beer significantly: mash temperatures.

mash temperature: checking temperature with a thermometer

Before going any further it’s useful to take a step back and look at what’s going in the mash.

Mashing

Brewers soak malt, usually made from barley, in warm water to extract sugar. This is mashing.

Malt is made by encouraging grains to start germinating before heating them to stop further growth. Malting produces enzymes capable of converting starch (inside the grain) into sugar.

Normally this conversion fuels the plant’s growth, but brewers use it to create sugary wort for fermentation into beer.

There are two types of starch in malted barley: amylose and amylopectin.
mash temperatures two types of starch in malted barley
Amylose is a simple chain of glucose molecules. Amylopectin is more complicated, taking the form of tree.

Malted barley has roughly 25% amylose and 75% amylopectin. I’ll get to the significance of reducing ends and non-reducing ends later in the post.

For the enzymes to work you need to activate them. This is done in warm water.

The temperature of that water determines which enzymes are brought to life, and what they do to your wort.

Enzymes

There are many enzymes in malt that take part in the mash.

However, rather than cover every eventuality and lose you in detail, the two I want to explain here are alpha-amylase and beta-amylase.

By focussing on these you’ll learn a simple rule of thumb that you can use to adapt your beer to your taste, or to suit the customs of a particular style.

Alpha-amylase

The first of these enzymes is alpha-amylase.
mash temperatures alpha-amylase action in mash
Alpha-amylase has these characteristics:

  • Active between 68.5 – 70°C (155 – 158°F)
  • Randomly breaks the glucose into chunks
  • It can’t separate amylopectin branches
  • Makes wort with high percentage of non-fermentables

Beta Amylase

The second enzyme to think about is beta-amylase.
mash temperatures beta-amylase action in mash
Beta-amylase has these characteristics:

  • Active between 60 – 65°C (140 – 149°F)
  • Turns non-reducing end into maltose (a fermentable sugar)
  • It can’t do anything with the amylopectin branches
  • Makes highly fermentable worts

The important thing to realise is that changing the temperature of the mash slightly means activating a different enzyme. The difference will manifest itself in the fermentabilty of the wort.

A more fermentable wort finishes with less residual sugar and a thin, light body. Less fermentable worts produce thicker, full bodied beers with more remaining sugars.

This is useful information if you’re trying to match the target final gravity for a given style of beer.

You can find more detail on enzymes and the mash process in this BYO article about mash temperatures or this one about extraction from Khymos.

Both are recommended reads.

Mash Temperatures Chart

Finally, I’ve condensed the above information into this simple chart:

single infusion mash temperatures for home brew

Mash temperatures: 60 – 65°C: More fermentable wort for dry, light beer; 68.5 – 70°C: Less fermentable wort for sweet, full bodied beers.

As usual, there is always room for more complexity. Once you get used to the effects of the different enzymes you can create multi-stage mashes that take advantage of more than one of them at the same time.

But for now just think about your mash temperature next time you brew, and let me know how you get on in the comments.

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Comments...

  1. Michael

    Have been brewing on and off for maybe twenty years with varying degrees of success, but have just recently discovered mashing and have just set up a Partial Mashing system (literally just bottled first 2 batches). In my research I have come across convoluted, sometimes conflicting info on the process. Your article, ‘A Simple, Illustrated Introduction To Single Infusion Mash Temperatures’, was what I had wished I had found earlier, good stuff! Cheers, M.

    • John

      Hi Michael, thanks for your comment.

      Putting the articles together helps me make sense of the various bits of information out there. I’m glad it’s of use to you as well.

      Good luck with the mashing!

  2. Andrew

    Does it make a difference in which order you do the alpha and beta rests?

    • John

      You should start cooler and work up.

  3. Paul

    Thanks for simplifying this and making it clear. This now explains why I have been thinking that I did a great job with very high efficiency to then find the fermentation would stop at 1025 to 1030 and nothing that I did would restart them. It’s obvious that 2 steps at 67 and 68c just produced lots of unfermentables where I was thinking I would get a higher ABV.

    • John

      Glad this was of use.

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